Electro adhesion device

ABSTRACT

The invention provides an electro-adhesion device ( 10 ) including a base ( 12 ) and first ( 14 ) and second ( 16 ) banks of thin electrically conductive electrodes ( 18 ) located apart from each other on a side of the base ( 12 ). The electro-adhesion device ( 10 ) also includes an insulating cover ( 20 ) over the first ( 14 ) and second ( 16 ) banks so that the outer side of the insulating cover ( 20 ) defines an electro-adhesion surface so that, in use, when the electrodes ( 18 ) are energized and an object to be attracted is placed adjacent the insulating cover ( 20 ), the object is attracted to the insulating cover ( 20 ) by a suitably high adhesion force. An outer surface ( 24 ) of each of the electrodes ( 18 ) has a linear border on one side and a sinusoidal border on an opposite side so that the width of each electrode ( 18 ) varies sinusoidally lengthwise along the electrode ( 18 ).

CROSS-REFERENCE TO RELATED APPLICATION

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/ZA01/00079 which has an Internationalfiling date of Jun. 13, 2001, which designated the United States ofAmerica.

FIELD OF THE INVENTION

This invention relates to an electro-adhesion device.

BACKGROUND TO THE INVENTION

Electro-adhesion is the process of creating a charge in an object andthereby attracting it to a special surface. Electro-adhesion devices,for attracting a non-magnetic object such as paper, have not beenintroduced as consumer products due to the fact that they are eitherineffective, in that they do not create a sufficient adhesion force, orvery expensive to make due to the complexity of these devices.

A further problem is that it is very difficult to create one adhesiondevice that attracts objects of a variety of materials with suitableforce. It is this application of the invention which shouldpredominantly but not exclusively be borne in mind.

SUMMARY OF THE INVENTION

According to the invention there is provided an electro-adhesion devicewhich includes

a base; and

at least two thin electrically conductive electrodes located apart fromeach other on the base so as to define an electro-adhesion surface sothat, in use, when the electrodes are energised and an object to beattracted is placed adjacent the electro-adhesion surface, the object isattracted to the electro-adhesion surface by a suitably high adhesionforce.

The electrodes may be located on one side of the base so that adjacentelectrodes form an electrode pair, which electrode pair is energised, inuse, so as to be oppositely polarised thereby causing a chargedifferential in a part of the object adjacent that electrode pair whichin turn causes the object to be attracted to the electro-adhesionsurface.

The electrodes may be located on opposite sides of the base when thebase is made of a substance having a high dielectric constant (Epsilon),typically of at least 5. Electrodes of an electrode pair may be locatedon opposite sides of the base, which electrode pair is energised, inuse, so as to be oppositely polarised thereby causing a chargedifferential in a part of the object adjacent that electrode pair whichin turn causes the object to be attracted to the electro-adhesionsurface. Electrodes on the same side of the base may be oppositelypolarised to electrodes on the opposite side of the base therebyincreasing a maximum withstand voltage between electrodes.

Each of the electrodes may have an outer surface facing away from thebase which outer surface defines at least a part of the electro-adhesionsurface and which outer surface has dimensions in any direction greaterthan the distance from such outer surface to the base, which distance isthe thickness of the electrode. The electrode is typically extremelythin so as to limit charge build-up between adjacent electrodes. Theelectrodes are typically less than 5 μm thick.

The electrodes may be silkscreen electrodes. The electrodes may bevapour deposition electrodes.

The electro-adhesion device may be configured so that as little air aspossible is trapped between adjacent electrodes.

The electrodes may be elongate electrodes located substantially parallelto each other on a side of the base.

Adjacent electrodes may be located apart from each other by a minimumdistance which is related to a maximum withstand voltage between theelectrodes before flashover occurs. As the electro-adhesion force isproportional to the voltage between an electrode pair, the minimumdistance may be selected so that an appropriate voltage is accomplishedbetween an electrode pair in order to accomplish a sufficientelectro-adhesion force without flashover occurring. Adjacent electrodesmay be located apart from each other by a fixed or varying distancegreater than or equal to the minimum distance.

The electrodes may be shaped to limit sharpness of corners of theelectrodes thereby reducing the possibility of flashover occurring.

The shapes of the outer surfaces of the electrodes may be selecteddepending on the material composition of the object to be attracted.

The electrodes of at least one electrode pair may have outer surfaceshaving large surface areas in order to attract metals. Typically, theelectro-adhesion device for metals only includes two oppositelypolarised electrodes separated by a single separation gap between them.

The electrodes of at least one electrode pair may have outer surfaceshaving small surface areas in order to attract non-metals.

The outer surfaces of the electrodes may be shaped so that they havevarying surface areas so that, in use, the object to be attracted may bemade from any one of a variety of materials including metals andnon-metals, the object thereby being attracted with suitableelectro-adhesion force regardless of the material. The varying surfacearea of the electrodes may be repetitive lengthwise along theelectrodes. The outer surface of at least two of the electrodes may havea linear border on one side and a sinusoidal border on an opposite sideso that the width of each electrode varies sinusoidally lengthwise alongthe electrode. Accordingly, the electrodes may be configured so that thesinusoidal border of one electrode is aligned adjacent the sinusoidalborder of an adjacent electrode and so that the linear border of oneelectrode is aligned adjacent the linear border of an adjacentelectrode, such that the minimum distance between adjacent electrodesremains fairly constant.

Typically, the electrodes of an electrode pair are oppositely polarisedby a low current with a relatively high voltage. The electrodes may bepolarised by way of a DC voltage. The low current is typically less than5 μA DC and the relatively high voltage more than 1500 V DC.

The base is typically made of a substance chosen to minimise leakagefrom the electro-adhesion device such as a substance having a high bulkresistivity of at least 10¹⁶ Ω/m.

The electro-adhesion device may comprise at least one layer formed byelectrodes and a layer formed by the base. Accordingly the base may bethin so as to define a layer of the electro-adhesion device.

The profile of the base on which the electrodes are located typicallydetermines the profile of the electro-adhesion surface. Accordingly, theprofile of the base on which the electrodes are located may be shaped soas to correspond to the shape of a portion of the object to beattracted, which portion is the portion which is placed adjacent theelectro-adhesion surface. This serves to minimise, in use, air gapsbetween the electro-adhesion surface and the object to be attracted.

In a preferred embodiment of the invention, the profile of the base onwhich the electrodes are located is typically flat, but in others it mayfollow any profile.

The base on which the electrodes are located is typically smooth. Suchsmoothness may be defined as having a surface variation of less than0.01 μm.

The electro-adhesion device may include an insulating cover over theelectrodes so that an outer side of the insulating cover defines theelectro-adhesion surface. The cover is typically as thin as possible asthe electro-adhesion force is inversely proportional to the distancebetween the electrodes and the object to be attracted. The cover may bethinner than 100 μm.

The cover may be in the form of a thin film. The film may be applied asa laminate.

The cover may be in the form of a coating. The coating may be applied asa spray on, dip in, or any other suitable means of application.

The cover is typically made from a substance having a high surfacerelative resistivity. The resistivity is typically more than 10¹⁶ Ω.

The cover may be made of a substance having a high dielectric constant(Epsilon), typically of at least 6.

The cover may be smooth. Such smoothness may be defined as having asurface variation of less than 0.01 μm.

The base may be in the form of an insulating cover as described above.Accordingly the electrodes may be sandwiched between two covers so thatthe electro-adhesion device includes two electro-adhesion surfaces.

The invention is not limited to the specific embodiments contained inthis specification and all variations falling within the spirit of theinvention are included in the scope of the invention as if specificallylisted.

DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of illustration only, withreference to the accompanying non-limiting diagrams in which

FIG. 1 shows a schematic representation, in three-dimensional view, ofan electro-adhesion device in accordance with the invention;

FIG. 2 shows a schematic representation, in side view, of theelectro-adhesion device of FIG. 1;

FIG. 3 shows a schematic representation, in three-dimensional view, ofan electro-adhesion device, having a base in the form of an insulatingcover, in accordance with the invention; and

FIG. 4 shows a schematic representation, in side view, of theelectro-adhesion device of FIG. 3; and

FIG. 5 shows a schematic representation of a bank of electrodes of anelectro-adhesion device in one embodiment of the invention, wherein theouter surfaces of the electrodes are shaped so that they have varyingsurface areas so that, in use, the object to be attracted may be madefrom any one of a variety of materials including metals and non-metals.

Referring to the drawings and FIGS. 1 and 2 in particular, referencenumeral 10 generally indicates an electro-adhesion device in accordancewith the invention. The electro-adhesion device 10 includes a base 12and first 14 and second 16 banks of thin electrically conductiveelectrodes 18 located apart from each other on one side of the base 12.The electro-adhesion device 10 also includes an insulating cover 20 overthe first 14 and second 16 banks so that the outer side of theinsulating cover 20 defines an electro-adhesion surface so that, in use,when the electrodes 18 are energised and an object to be attracted isplaced adjacent the insulating cover 20, the object is attracted to theinsulating cover 20 by a suitably high adhesion force.

Accordingly, the electro-adhesion device 10 comprises a layer formed byelectrodes 18 and a layer formed by the base 12, wherein the base 12 isthin so as to define a layer of the electro-adhesion device 10.

The first 14 and second 16 banks are separated by a gap 22 which is assmall as possible to prevent charge build-up between the banks 14, 16.

The base 12 is typically made of a substance chosen to minimise leakagefrom the electro-adhesion device 10 such as a substance having a highbulk resistivity of at least 10¹⁶ Ω/m.

The profile of the base 12 determines the profile of theelectro-adhesion surface. Accordingly, the profile of the base 12 isshaped so as to correspond to the shape of a portion of the object to beattracted, which portion is the portion which is placed adjacent theelectro-adhesion surface. This serves to minimise, in use, air gapsbetween the electro-adhesion surface and the object to be attracted.

In this embodiment of the invention, the profile of the base 12 is flat,but it is to be understood that in other embodiments of the invention,the profile of the base 12 may follow any profile.

The base 12 is typically smooth having a surface variation of less than0.01 μm.

The insulating cover 20 is as thin as possible as the electro-adhesionforce is, amongst other factors, inversely proportional to the distancebetween the electrodes 18 and the object to be attracted. The cover 20is typically thinner than 100 μm.

The cover 20 is made from a substance having a high surface relativeresistivity of typically more than 10¹⁶ Ω and having a high dielectricconstant (Epsilon), typically of at least 6. The cover 20 is typicallymade from a polymer such as nylon 6 or PVC based substance.

In certain embodiments of the invention, the cover 20 is in the form ofa thin film which is applied as a laminate. In other embodiments, thecover 20 is in the form of an enamel coating applied as a spray on, dipin, or any other suitable means of application.

The cover 20 is smooth with a surface variation of less than 0.01 μm.

With particular reference to FIGS. 3 and 4, reference numeral 10.1generally indicates an electro-adhesion device in accordance withanother embodiment of the invention. The electro-adhesion device 10.1substantially resembles the electro-adhesion device 10 and, accordingly,like reference numerals have been used to indicate the same or similarfeatures unless otherwise indicated. In this embodiment of theinvention, the base is in the form of an insulating cover 20.1 asdescribed above. Accordingly the banks 14, 16 are sandwiched between twocovers 20, 20.1 so that the electro-adhesion device 10.1 includes twoelectro-adhesion surfaces.

FIG. 5 shows a bank 14/16 of elongate electrodes 18 substantiallyparallel to each, in accordance with a preferred embodiment of theinvention. Adjacent electrodes 18 form an electrode pair, whichelectrode pair is energised, in use, so as to be oppositely polarisedthereby causing a charge differential in a part of the object adjacentthat electrode pair which in turn causes the object to be attracted tothe electro-adhesion surface.

Each of the electrodes 18 has an outer surface 24 facing away from thebase 12 which outer surface 24 has dimensions in any direction greaterthan the distance from such outer surface 24 to the base 12, whichdistance is the thickness of the electrode 18. Each electrode 18 istypically extremely thin so as to limit charge build-up between adjacentelectrodes 18. Each electrode 18 is typically less than 5 μm thick.

The electrodes 18 are typically silkscreen electrodes or vapourdeposition electrodes.

The bank 14/16 is configured so that as little air as possible istrapped between adjacent electrodes 18.

Adjacent electrodes 18 are located apart from each other by a fixedminimum distance 26 which is related to a maximum withstand voltagebetween the electrodes 18 before flashover occurs. As theelectro-adhesion force is proportional to the voltage between adjacentelectrodes, the minimum distance 26 is selected so that an appropriatevoltage is accomplished between an electrode pair in order to accomplisha sufficient electro-adhesion force without flashover occurring.

The electrodes 18 are shaped to limit sharpness of corners of theelectrodes 18 thereby reducing the possibility of flashover occurring.

The shapes of the outer surfaces 24 of the electrodes 18 are selecteddepending on the material composition of the object to be attracted.

In order to attract metals the electrodes 18 would have outer surfaces24 having large surface areas. Typically, the electro-adhesion device10, 10.1 for metals only includes two oppositely polarised electrodes 18separated by a single separation gap 22 between them.

In order to attract non-metals, the electrodes 18 would have outersurfaces 24 having small surface areas.

In this embodiment of the invention, the outer surfaces 24 of theelectrodes 18 are shaped so that they have varying surface areas sothat, in use, the object to be attracted may be made from any one of avariety of materials including metals and non-metals, the object therebybeing attracted with suitable electro-adhesion force regardless of thematerial. Accordingly, the outer surface 24 of each of the electrodes 18has a linear border on one side and a sinusoidal border on an oppositeside so that the width of each electrode 18 varies sinusoidallylengthwise along the electrode 18 whereby the varying surface area ofeach electrode 18 is repetitive lengthwise along the electrode 18.Accordingly, the electrodes 18 are configured so that the sinusoidalborder of one electrode 18.1 is aligned adjacent the sinusoidal borderof an adjacent electrode 18.2 and so that the linear border of oneelectrode 18.1 is aligned adjacent the linear border of an adjacentelectrode 18.3, such that the minimum distance 26 between adjacentelectrodes 18 remains fairly constant.

It is to be appreciated that the linear border of one of the endelectrodes 18 of the first bank 14 is located parallel to the linearborder of one of the end electrodes 18 of the second bank 14 on the base12 so as to form the gap 22.

It is also to be appreciated that in other embodiments of the invention,the electrodes 18 may be shaped and configured so that certain portionsof the electro-adhesion surface attract only metals, other portionsattract only non-metals and still other portions attract both metals andnon-metals or any combination of two of these portions.

Typically, the electrodes 18 of an electrode pair are oppositelypolarised by a low DC current, typically less than 5 μA DC, with arelatively high DC voltage, typically more than 1500 V DC.

It is further to be appreciated that in another embodiment of theinvention, the electrodes 18 may be located on opposite sides of thebase 12 when the base 12 is made of a substance having a high dielectricconstant (Epsilon), typically of at least 5. Electrodes 18 of anelectrode pair may be located on opposite sides of the base 12, whichelectrode pair is energised, in use, so as to be oppositely polarisedthereby causing a charge differential in a part of the object adjacentthat electrode pair which in turn causes the object to be attracted tothe electro-adhesion surface. Electrodes 18 on the same side of the base12 may be oppositely polarised to electrodes 18 on the opposite side ofthe base 12 thereby increasing the maximum withstand voltage betweenelectrodes 18 and reducing the effect of impurities on theelectro-adhesion surface. It is to be appreciated that the electrodepair in this embodiment of the invention has all the samecharacteristics of an electrode pair as described with reference to thedrawings except that one electrode 18 of the electrode pair is locatedon an opposite side of the base 12. Accordingly, the transverserelationship of the electrodes 18 of an electrode pair is altered butnot the planar relationship with respect to the electro-adhesionsurface.

It is believed that an advantage of the invention is that a whole rangeof cost effective and viable electro-adhesion devices can be designed,manufactured and sold. It is further believed to be an advantage that awide range of objects are attracted to the electro-adhesion device withadequate force to be retained in place on an electro-adhesion surface ofthe device.

What is claimed is:
 1. An electro-adhesion device which includes: a base; and at least two thin electrically conductive electrodes located apart from each other on the base to form at least one electrode pair defining an electro-adhesion surface, wherein outer surfaces of the electrodes of at least one of the electrode pairs are shaped to have varying surface areas so that, in use, when the electrodes are energized and an object to be attracted is placed adjacent the electro-adhesion surface, the object is attracted to the electro-adhesion surface by a suitably high adhesion force regardless of the type of material from which the object is made and, accordingly, the object to be attracted may be made from any one of a variety of materials including metals and non-metals.
 2. An electro-adhesion device as claimed in claim 1 wherein the electrodes are located on one side of the base so that adjacent electrodes form an electrode pair, which electrode pair is energized, in use, so as to be oppositely polarized thereby causing a charge differential in a part of the object adjacent that electrode pair which in turn causes the object to be attracted to the electro-adhesion surface.
 3. An electro-adhesion device as claimed in claim 1, wherein the electrodes are located opposite sides of the base when the base is made of a substance having a high dielectric constant (Epsilon).
 4. An electro-adhesion device as claimed in claim 3, wherein electrodes on the same side of the base are oppositely polarized to electrodes on the opposite side of the base thereby increasing the maximum withstand voltage between electrodes.
 5. An electro-adhesion device as claimed in claim 1, wherein the electrodes are silkscreen electrodes.
 6. An electro-adhesion device as claimed in claim 1, wherein the electro-adhesion device is configured so that as little air as possible is trapped between adjacent electrodes.
 7. An electro-adhesion device as claimed in the claim 1, wherein shapes of the outer surfaces of the outer surfaces of the electrodes are selected depending on the material composition of the object to be attracted.
 8. An electro-adhesion device as claimed in claim 1, wherein the varying surface area of the electrodes is repetitive lengthwise along the electrodes.
 9. An electro-adhesion device as claimed in claim 1, wherein the outer surfaces of the electrodes have a linear border on one side and a sinusoidal border on an opposite side so that the width of each electrode varies sinusoidally lengthwise along the electrode.
 10. An electro-adhesion device as claimed in claim 9, wherein the electrodes are configured so that the sinusoidal border of one electrode is aligned adjacent the sinusoidal border of an adjacent electrode and so that the linear border of one electrode is aligned adjacent the linear border of an adjacent electrode, such that the minimum distance between adjacent electrodes remains fairly constant.
 11. An electro-adhesion device as claimed in claim 1, wherein the electrodes of an electrode pair are oppositely polarized by a low current with a relative high voltage.
 12. An electro-adhesion device as claimed in claim 1, which comprises at least one layer formed by electrodes and a layer formed by the base, wherein the base is thin so as to define a layer of the electro-adhesion device.
 13. An electro-adhesion device as claimed in claim 1, wherein the profile of the base on which the electrodes are located is shaped so as to correspond to the shape of a portion of the object to be attracted, which portion is the portion which is placed adjacent the electro-adhesion surface.
 14. An electro-adhesion device as claimed in claim 1, wherein the electro-adhesion device includes an insulating cover ova the electrodes so that an outer side of the insulating cover defines the electro-adhesion surface.
 15. An electro-adhesion device as claimed in claim 14, wherein the cover is in the form of a thin film.
 16. An electro-adhesion device as claimed in claim 14, wherein the cover is in the form of a coating.
 17. An electro-adhesion device as claimed in claim 14, wherein the cover is made from a substance having a high surface relative resistivity.
 18. An electro-adhesion device as claimed in claim 14, wherein the cover is made of a substance having a high dielectric constant (Epsilon).
 19. An electro-adhesion device as claimed in claim 14, wherein the base is in the form of at least a part of the insulating cover.
 20. An electro-adhesion device as claimed in claim 19, wherein at least some of the electrodes are sandwiched between the two covers so that the electro-adhesion device includes two electro-adhesion surface. 